Variable-speed electric motor.



J. C. LINCOLN.

VARIABLE SPEBD'BLBGTRIG MOTOR.

APPLICATION FILED MAR.14, 1906.

1,043,325 Patented Nov. 5, 1912.

Ina/527m?,

Jahn LZHCUZH l :g UNiTED srArEs PATENT OFFICE.

JOHN LINCOLN,

or EAST CLEVELAND, oHIo, Assieivon 'ro "iHE LINCOLN COMPANY,

E CLEVELAND, oHIo, A CORPORATION or omo. '1

VARIABLE-SIIIEED ELECTRIC MOTOR.A

ble o obtaining wide variations in speed,

while Ibeing simple, cheap and compact in construction, and economical,eflicient and durable inoperation.

To1 this end, my improved motor conforms to a .large extent to generallyaccepted standards in the design of dynamo-electric machinery, butcontains in addition, certain features which are pointed out in thefollowing specification and claims, and which secure wide variations inspeed, while avoiding certain undesirable features hitherto observed inmot-ors of this general t pe.

The most common method o' securing variation in speed of an electricmotor, is by cutting resistance into circuit with the field-windingsthereof, but high speeds are impracticable with a construct-ion of thistype, except where means are provided for preventing sparking at thebrushes. This `result may be accomplished by employing.

a special field construction supplying a commutating field of force forthe armature, the

windings lof said commutating Held-struc-` ture being in series relationwith the armature, but this arrangement involves the highly undesirablefeature of making the roportional to the speed of the armature ighspeeds. That load when operating at is, the speed will increase as theload comes on, instead of remaining constant. Accord ingly', lI haveimproved upon this construction to" the extent of entirelyv eliminatingthe use of regulating resistance for the fieldwindings, by employing atraveling brush or brushes, betweenl which the currents for the shuntfield-windings are taken from the commutator of the 'armature at varyingpotentials, and under conditions obtaining a decrease in speed directlyproportional with the load, whereby the speed of the armature isaccurately governed, and the defective operation above alluded to iscounteracted or overcome. Preferably, I employ two Specification ofLetters `Patent.

Application tiled-March 14', 1906.v Serial No. 306,023. i l

traveling brushes, which are associated with suitable contacts, tosecure the reversalof current throughthe field-windings. and avoid theeffects' of distortion upon the eX.- citing current ordinarilyobservable in motors of this general type. With this construction,embodying two concurrently moving brushes, it is possible to equi themotor so that not only are eiects` of distortion practicallyeliminated', but the lincrease 'of speed under heavy loads may beavoided as well. Means may also be provided inV my improved motor foravoiding the use of starting resistance, found in speciallv connectedstarting-coils provided upoii the field-structure in series relationwith the armature, which, for a brief period, take an abnormally largecurrent to give the armature an initial impulse, and then are cut out ofcircuit during the operation of the motor.l All the foregoing operationsmay be controlled by the same controllermechanism, also of my invention,and herein set forth, together with certain other structural featureswhich will be made clear by referring to the accompanying drawingsPatented Nv. 5, 1912. 'i

forming a part of this specification, wherei Figure I. is 'a sideelevation of an electric motor embodying my invention, wherein thesupportingarms or spider, connected with the .field structure, are shownbroken away, and a vfew of the parts are depicted in section, for thepurpose of better illustrating my limproyements. Fig. II. is a verticalsectional view of the commutator end of my improved motor. Fig. III. isa diagram setting forth the Connections, and indicating the electricalrelation of the parts of said motor. Fig. IV. is a detail showing a partof the manually-operated controlling-mechanism; Fig. V. is anotherdetail'illustrating, upon enlarged scale, the automaticallyoperatedswitch for connecting and disconnecting .the starting-coils; and Fig.VI. is a detail view illustrating means for-securing the unequalmovement ofthe traveling brushes.

Throughout each ofthe several figures of the drawings, I have employedthe same character of reference to indicate similar parts, in order toavoid any confusion or misunderstanding.

.Referring first to Fig. I., it will be seen that thefineld-structure lof this particular fio motor is provided with tour main polepieces Q,and two interposed supplemental or commutating pole-pieces 3, withinwhich field-structure the armature a is adapted to rotate, preferablyupon ball -bearings 5. Shunt windings 6 are positioned upon the mainpole-pieces 2, and series windings T are provided upon the commutatingpole pieces 3, while, in addition, series startingcoils 3 are superposedupon two ot the diametricallypositioned pole-pieces 2, which 1temporarily in series relation with the a nature, and the coils orwindings 7,

initially, current a'iproximating tull load current, will flow throughl' J and serve to the arma- 1., onotally mounted switch 9', comtheduplicate blades 10, 11, adapted alternately to engage paired contacts1Q, 13, 14, or 15, is provided for autrmiatically controlling saidstarting-coils, which, referred to above, avoid the necessity' :toreinploying a resistance-bor in starting the motor.

The main brushes oit t-he motor are designated as 16 and l?, which areconnected, as shown in Fig. Hl., with the leads ot the en ergi ngcircuit of constant potential. Shaft 18, extending through one ot thearms ot' the spider or support, at one side oit the motor, carriesexteriorly, the handwhecl 19, and interiorly, the pinion 20, whichlatter en gages the toothed segment 9.1, and a second pinion 22, meshingin turn with another' toothed segment 23. These segments are thus maderotatable in opposite directions by means ot the hand-wheel, and respectively carry the movable brushes 25 with in their mountings, and,moreover e spur or tooth 26', is provided upon seg .1, for concurrentlyactuating the pivoted switch 9. These brushes 2l, 25, preferably are so`nanrow thatl they will simply span the insulation between two ot' thecommutator seg ments, being one-sixteenth an inch in thickness, or equalto twice the width o1 such insulation in one of my improved nio-- tors,as compared with main brushes ot onev halt inch thickness. Associatedwith these traveling brushes, are segmental contacts 26, 27, 28 and29,the alternate contacts of which are connected with each other, whilethe shunt tield-windings 6 are connected bc tween the adjacent cont-acts2? and 9.8; thus providing means tor supplying current from the armaturethrough said shunt field windings in either direction and ot varyingpotentiel, in order to secure the rotation and reversal oit the armatureat all ot its varying speeds within the range of the motor. Theseelectrical connections will be very readily gathered by making referenceto the diagram of Fig. Ul. Preferably, the main pole-pieces 2 arelaterally slotted or channeled at 31, in order to increase the airgap inthis position, tor a purpose which will be later explained; although theordi nary segmental polar tace indicated in Fig. IH., may be employed.

1n F ig. V., appears an enlarged view oit the automatically-actuatedswitch for controlling the starting-coils, which comprises the blades10, 11, one of which is shown mounted in the pivoted holder 32, by meansof insulation 33 in position to be swung into engagement with any of thepaired contacts 12, 13, 14 and 15, to etiect the circuit changesconventionally indicated in the diagram. The lower portion of the holder32 is recessed at 34, and is adapted to be engaged by the tooth or spur26', carried upon segment 21, in order that the switch 9 may beautomatically actuated to cut the series startingcoils intofand out ofcircuit upon the actuation oi hand-wheel 18; it being apparent thestarting-coils are concerned, uponthrowing the switch either to theright or the lett, as will occur when operating the mot-or in onedirection or the other. In order to cenler the switch, a detent in theform ot a roller 3G, carried at the end ot a springactuated arm 3T, isadapted to engage a recess 38, provided upon the mounting for the switchblades, whereby the switch will be hold in normal position midwaybetween paired contacts 13'and 1/1, at all times when the motor is notrunning; while said rollers may be caused to ride upon one or the otherot curved edges 39 ot the plate, when the switch blades are inengagement with either set of contacts.

For the purpose ot e'rplainingthe opera tion ot my improved motor,reference will now be had to the diagrammatic figure, setting forth inconciso torni, the electrical teatures thereof. Normally the travelingbrushes 25, between which the shunt field-windings are adapted to beconnected, stand at an angle ot ninety degrees with re spect to eachother, and in this position are disconnected from their segmentalcontact-s Q6 to 29. Assuming that the armature is to be' rotated in acloclrwise direction, the hand-wheel will be actuated to turn the switch9 to the lett, which will cause the brushes to diverge and respectivelyengage contacts 26 and. 29; while switch-blades or contacts 10, 11 willbe brought into en gagement with paired contacts 13, between which theseries' starting-coils 8 are provided. Current will' at once flow frommain conductor 3st 'to brush`16, through the windings oit armature 2,brush 17, to the ccmmutating' tield-windings 7, switch plate 10, the'iowermost of the paired contacts 13, the uppermost ot paired contacts14e, through the starting-coils 8, the uppermost of paired contacts 13and switchblade 11, to main conductor 35. This at that the sameoperation takes place, so far as current.

once supplies an initial starting torque for the armature, since currentapproximately equal to twice that supplied at full load, will passthrough the motor circuit above indicated. Y course, inefficientlypositioned yin the motor, and consequently cannot'serve in thiscapacity, although receiving the full flow of The speed of' the armatureunder the influence of the starting-coils, will immediately pick up, andcurrent will be generated in the windings of the armature,"

which will be conducted by brush 24, through connected contacts 26 and28 to the shunt windings 6 of the motor, and through con- .nectedcontacts 27 and 29 to brush 25, andv the armature windings,- thusexciting the shunt fields of the motor. The hand-wheel is then turned alittle farther to disconnect the starting-coils, but at firstshort-circuiting the switch-blades 10, 11 between the paired sets ofcontacts 12, 13, and then disconnecting the coils or windings 8 upon thecomplete throw of the switch. Circuit may then be traced from main 34,through brush 16, the windings'or armature 2, brush 17, the commutatingfield-windings 7 and shortcircuited switch-blades 10, 11,'to main 35,which is the normal running position of the motor. In order to increasethe speed at which the armature is driven, it is only necessary tocontinue the rotation of the handwheel in the saine direction, so thatthe brushes 24, 25 will. continue to diverge while in engagement withthe respective contactsy 26, 29, 'in order that they may subtend anincreasing arc of the commutator. This, as will be well understood,causes current of decreasing voltage to flow through the main or -shuntfield-windings 6, and, as a result, the magnetic .fiux into the armaturedecreases and the speed is correspondingly inn' creased. Initially,however, the movement of the brushes from their normal or neutralpositions, through the first ten or fifteen degrees of separat-ioncauses practically very little variation in the fiow of current throughthe much .as said brushes are so mounted` as to ,mutually diverge orconverge toward parts upon the commutator having less difference 'opotential, the speed of the armature is v very simply and easilyregulated thereby.

' -f windings are A.the brushes of the motor,

Il have provided between the main poles of At high speeds, however, itlis practically necessary to provide means for overcoming the sparkingwhich otherwise will occur at and, accordingly,

systems the motor, the secondary magnetic found lin, the pole-pieces3,-whichcarry the .series windings 7 Thereby the armature j, subjectedover restricted areas T'to'the lines of `magnetic forcey generated bythese secondary orcommutating magneticsystems, so that the armaturecoils at the The commutating fields, are, ofl

shunt field-windings; but inas-v moment of commutation have generatedtherein a counter electro-inotive force in op position to the currentpreviously `flowing therein, whereby the one tends to reverse the other,and sparking is prevented. These series wound coils, as previouslyadverted to, however, introduce into the motor the highly undesirablefeature of causing the speed to increase proportionately with theincrease in load, instead ofremaining constant under varying conditionsof load. To obviate this feature, I preferably design the shunt fieldstructure, in accordance with principles well understood in the art, sothat with equal movements of the brushes, the flux increases from ten tofifteen per-cent. as the load in. creases, and, 1n consequence, thetendency will be to cause the speed to decrease, which I have found issuflicient to overcome the above mentioned tendency of the speed toincrease under additional load. In other words, these two diversetendencies oppose one another in my improved motor, when properlydesigned, and the speed, in consequence, will remain as adjusted,practically constant under all varying loads.

Another important function'which I now desire to refer to, and which isof very great importance in variable speed electric motors of thisclass, is thedistortion effect which results at high speeds in the mainmagnetic field. This distortion depends upon the ratio between theampere turns in the field-windings and upon the armature, and since theformer are necessarily greatly reduced under high speed conditions, thelines of magnetic force tend to concentrate or bunch at those extremeedges of the main pole-pieces 2 which the armature is approaching, as at40, Fig. III., if we assume that the armature is rotating in a clockwisedirection. Consequently, the magnetic, field is very strong in suchpositions of approach, and becomes so weakened at the leaving oropposite edges of the pole-pieces 41, as to exhibit actual reversal ofpolarity under the -infiuence of the armature at high speeds.

Consequently, if a single traveling brush is employed to take off thevarying qui: rents for exciting the shunt fields, said brush must travelover a veryl large arc, and because of the distort-ion effect above.referred to, the field excitation would. vary vproportionately to suchdistortion, and, in

consequence, the speed control would be irregular and impracticable.This results from the fact that at high speeds, thetravel ing and itsco-acti'ng stationary brush would. lsubtend anfarc embracing one or theother of the extremities (ir-edges of a given pole- Apiece. As juststated, Athe leaving edge of such pole-piece would be very deficientlvexcited 'at high speeds under heavy load,

while the meeting edge wouldvbe correspondingly ovenexcited. Hence, ifthe brush subtended an are including the former, the voltage generatednecessarily lbe the opposite of the action just described.

Under this` extremity, the flux from the eX- tremity of the pole-pieceinto the armature would increase several hundred per-cent. at highspeeds, from no load to full load, thereby varying the current throughthe shunt iield to a corresponding degree. lt is clear that at highspeeds, excitation derived from a moving` brush and a co-actingstationary brush would be utterly impractical. My improved constructionovercomes -this'undesirable feature, by reason of the fact that thebrushes are mutually caused to diverge or approach preferably at equalrates of speed in securing regulation of the speed ot the motor, wherebyas one of said brushes is caused to approach or recede from the coilsunder excitation of the strongly excited field, the otherbrushcorrespondingly approaches or recedes from the coils under excitation ofa weakened and distorted magnetic tie-ld, and the one dis` toi-tingeffect exactly counterbalances the other. In other words, the use of twotraveling brushes causes the voltage to res main constant, by reason oftheir subtending a portion of the field which remains constant under allconditions of load. At high speeds, the moving brushes may approach eachother quite closely, and in consequence, a small movement of thetraveling brushes causes a considerable change in the current flowingthrough the shunt field, and a correspondingly large change in theresulting speed ot' the motor. In order to permit of a greater motion oftheinoving brushes when obtaining a given variation of speed, thecentral portions of the main field-poles 2 are laterally cut away, asshown at 31. This cutting away increases the airgap, and consequentlydecreases the fiux passing from the pole-piece into t-he armaturethrough the angle subtended by the cut-away portion, if the flux isdecreased tov one-halt its original value by this means, twice themotion of the moving brushes will be required to obtain a given changein speed, than would be required if the center ot the pole-piece was notcut away. This increased motion of the moving brushes in order to obtaina given change in speed, it is clear, will take place only when thebrushes are close enough together or far enough apart to subtend thatportion of the armature excited by the portion of the pole-piecewhich'is cut away.

Referring again to the connections shown in F ig. III., it will be seenthat my improved motor is equally Well adapted for operation in theopposite or contrafcloclc wise direction, and that corresponding resultsare obtained by reversing the direction of rotation of the hand-wheel,since the -only difference is to cause a reversal of current temporarilysupplied to the start ing-coils and a corresponding reversal ot currenttaken from the armature at various potentials between the brushes 25,26, and circulating through the shunt field-windings 6, all of thisbeing accomplished in the well known manner of supplying reversing;

switch connections for these parts as shown.

lVhile l have stated that the preferred construction of my improvedvariable speed electric motor is such that the traveling brushes shallhave equal movement toward or from each other, I desire now to explainin connection with the diagram, Fig. Ill., a feature of construct-ionand operation which lends itself to obtaining different results in thestructure of my invention. In said diagram, l have indicated by theright angle 43, 42, 44, the normal position of the brushes with respectto the exciting polepiece, and by the angle 45, 42, 4G, the position ofmaximum adjustment of said brushes, wherein the highest speed otA themotor will be attained. These angles, it is to be understood, areintended to indicate the position o i', or the arc subtended by the-brushes with respect to the electro-magnetic structure of the motor,rather than their bodily position. It is apparent, that by proportioningthe ninions 20, 22, as by giving the latter thirteen teeth, as opposedto twelve upon the former, it will be possible to cause the unequalrotation of the engaged segments 21, 23, and a correspondingly unequalmovement of the traveling brushes. As a result, the position of maximumadjustment of said brushes may be approxi* mately indicated by thedotted lines forming the angle 47, 42, 48, thereby causing the brushes24, 25, to subtend an arc embracing armature coilsv excited by theweakened and distorted field represented by portion 41 ot thepole-piece. This will cause a decrease in tiux as compared with thatobtained when the brushes subtend an arc represented by the angle 45,42, 46, and the result will be an increase ot speed proportional to suchdecrease in flux as the load comes on. In other words,l' y causing oneof the brushes yto travel more rapidly in the direction of rotation ofthe armature as compared with llt imagen movement of the other, adistinctly different result is obtained than before, wherein the motoris equipped, as described, to secure a small counteracting drop in speedthrough the brush adjustment as the load comes on. This, and other of myimprovements, may be applied to dynamo electric machines differingsubstantially from the variable speed motor which I have selected asenabling me best to explain my invention.

The illustration which I have above given, although representing anexperimental modification of one of my improved motors, should'beunderstood as being merely typical, and arbitrarily selected toipdicat'e the result obtainable by securing unequal movement of thebrushes. It will be understood that an unequal movement of the brushesin a reverse direction will secure 'corresponding results, with reversalof the s armatures `rotation, or opposite results without such reversalof rotation.'

.From a consideration of the foregoing, it will lbe appreciated .that Ihave improved upon the variable speed electric motor, by equipping thesame with Aconcurrently traveling brushes to neutralize the effects ofdistortion upon the magnetic field thereof, observable athighv speeds,and have counter-acted the tendency of the commutating or interpolarmagnetic system to increase the speed under increasein load, bycombining therewith means for correspondingly affecting the motor todecrease its speed under similar conditions; this means being present inthe design of the motor to cause an increased flux from thefield-structure to the armature with an increased load. However, Idesire to be understood that my invention is in'no wise restricted tothis' corrective feature, since the motor yof my invention is equallycapable of design whereby the flux will remain substantially constantunder var ing loads at any given speed, to which en the mutuallytraveling brushes are ada ted to supply current of proper potential) tothe shunt field windingls.

Having now described a variab e. speed equipped with vshunt windings, ofan armature mounted to rotate within said field-'- structure, stationarybrushes'and two mutually traveling brushes engaging the commu tator ofsaid armature, mechanism for effectin the concurrent movement of saidtraveling brushes toward or from each electric motor embodyin myimprovements,A

other, wherebyl the ,current inl the shuntv field-windings connectedwith said brushes may be maintained at-constant values in any of thepositions of ladjustment dof ".said. brushes, and switch contactsassociatedwith said brushes for effecting the reversal of currentthroughout the shunt field-windings, substantially as set forth.

2. In a variable speed electric motor, the combination with a compositefield-structure consisting of main `poles normally ex- ,cited'by shuntwindings and equipped with series windings or starting-coils, of anarmature mounted to rotate within' said fieldstructure traveling brushmechanism engaging the commutator of said armature and connected tosupply current through the shunt field-windings, a secondary switch forcutting the series starting-coils into and out of circuit, and means foractuating the traveling brush mechanism and concurrently moving saidswitch to connect and disconfnect the starting-coils, substantially asset forth. a

3. In a variable speed electric motor, th combination with a compositefield-structure consisting of main poles normally' excited by shuntwindings and equipped with series windings or starting-coils, of anarmature mountedl to rotate within said :fieldstructure, traveling brushmechanism engaging the commutator of said armature and lconnected tosupply, current through the shunt field-windings, reversing-switchcontacts positioned to be engaged by said traveling brush mechanism foreffecting the reversal of current through the vshunt fieldwindings asthe brushes are moved in one direction or the other, a secondary switchfor cutting the series starting-coils into and out of circuit, and meansfor actuating the traveling brush mechanism and concurrently moving saidswitch to connect and discon-y nect the starting-coils, substantially asyset forth. a

4. Inapparatus .of the class described the combination with a lmagnetic.field-struc ure' or system', and its armature mounted to rotate therein,of traveling brush mechanism engaging the commutator of the motor com-Aprlsing narrow brushes bearing upon the contact-bars thereof, twotoothed segments rotatably mounted and respectively carrying thebrush-holders, and two meshing pinions respectively engaging.' thesegments' and adapted to actuate said segments and brushes to move inopposite directions; sub-. stantially as set fort .f l

5. In apparatus of the class described, the combination with a magneticfield-structure or system, and its armature mounted to rotate therein,of traveling brush mechanism engaging the commutator of the motorcomprising narrow brushes bearing upon the contact-bars thereof, twotoothed segments rotatably mounted and respectively carrying thebrush-holders, two meshing pinions respectively engaging the segmentsand adapted to actuate said segments and brushes to move in oppositedirections, and an auxiliary switch associated with one of said movingsegments whereby said switch is concurrently actuated at predeterminedperiods during the movement of the brushes, substantially as set forth.

6. In apparatus of the class described, the combination with a magneticfield-structure or system, and its armature mounted to rol tate therein,of traveling brush mechanism engaging the commutator of the motorcomprising narrow brushes bearing upon the contact-bars thereof,reversing-switch contacts associated with said traveling brushes andadapted alternately to be electrically engaged by said brushes dependentupon the direction of movement thereof, two toothed segments rotatablymounted and respectively carrying the brush-holders, and two meshingpinions respectively engaging the segments and adapted to actuate saidsegments and brushes to move in opposite directions, substantially asset forth.

7. in a dynamo electric machine, the combination with theield-structure, of an armature mounted to rotate therein, saidfieldstructure having its polar-faces laterally channeled or cut-awaythroughout restricted areas presented to the armature, whereby theair-gap is materially increased over such areas, and traveling brushmechanism associated with the armature and adording an increased path ofmovement for adjustment in the positions corresponding to the channeledpolar-faces, substantially as set forth.

8. ln a` variable speed electric motor, the combination with a mainfield-structure provided with windings in shunt relation with the'armature and. series windings or starting-coils, narrow auxiliary polesprovided with series windings and positioned between the main poles,narrow traveling brushes engaging the commutator of the armature betweenwhich the shunt windings are connected, a switch for connecting anddiscon necting the starting-coils, and mechanism for concurrentlycontrolling the switch and effecting the mutual travel of the aforesaidbrushes, substantially as set forth.

9. In a dynamo electric machine, the combination with thefield-structure thereof equipped with shunt field-windings, an armaturemounted to rotate within said field -v structure, two traveling brushesforming the terminals of the shunt field-windings, and means foreffecting the concurrent and unequal travel of said brushes in oppositedirections upon the commutator of the armature, whereby thefieldexcitation and the iux tothe armature may be varied, substantially asset forth.

l0. In a dynamo. electric machine, the

combination with the ield-structure thereof equipped with shuntheld-windings, an armature mounted to rotate within said fieldstructure,two traveling brushes forming the terminals of the shunt field-windings,means for electing the vconcurrent and unequal travel of said brushes inopposite directions upon the commutator of the armature, whereby thefield excitation andthe flux to the armature may be varied, and meansfor subjecting restricted areas of the armatureto a commutating field toavoid sparking at the brushes under conditions of heavy load,

4substantially as set forth.

Signed at Cleveland, this 12th day Vof March, A. D. 1906, in thepresence of two subscribing witnesses.

JOHN C. LINCOLN.

Witnesses:

EDWARD H. WALSH, J. D. MALLOY. v

